Reorientation during Body Turns

Immersive virtual environment (IVE) systems allow users to control their virtual viewpoint by moving their tracked head and by walking through the real world, but usually the virtual space which can be explored by walking is restricted to the size of the tracked space of the laboratory. However, as the user approaches an edge of the tracked walking area, reorientation techniques can be applied to imperceptibly turn the user by manipulating the mapping between real-world body turns and virtual camera rotations. With such reorientation techniques, users can walk through large-scale IVEs while physically remaining in a reasonably small workspace. In psychophysical experiments we have quantified how much users can unknowingly be reoriented during body turns. We tested 18 subjects in two different experiments. First, in a just-noticeable difference test subjects had to perform two successive body turns between which they had to discriminate. In the second experiment subjects performed body turns that were mapped to different virtual camera rotations. Subjects had to estimate whether the visually perceived rotation was slower or faster than the physical rotation. Our results show that the detection thresholds for reorientation as well as the point of subjective equality between real movement and visual stimuli depend on the virtual rotation angle.